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Two procedures developed by the present authors are applied to evaluatecrack closure for structural steel. One of these (the A method) involves operations onelectric signals from the load and local strain transducers, whilst the other (the D method)applies processing of the digitized compliance data. The closure levels are identified basedon comparisons between the open crack compliance variations upon loading andunloading. Specially designed fatigue tests were conducted to generate fatigue crackgrowth data and compliance data necessary to check the performance of both methods.Parameters of the compliance data acquisition were found to significantly affect the closurelevels according to the D method. For a properly chosen combination of these parameters,the D method results compare well with those from the A method obtained using a differentmeasurement system and assumed to represent the true closure levels. The adequacy ofboth methods is proved by the ability of the resulting effective stress intensity factor rangeto correlate the observed effects of stress ratio on fatigue crack growth and to account forthe post-overload transient crack growth behaviour.